Arc-suppressing multiposition electric switch



'Jan. 12,1965 J. L. MGCLURE 3,155,598

ARC-SUPPRESSING MULTIEOSITION ELECTRIC swncn Filed Aug. 14, 1961 2Sheets-Sheet 1 f g': .L f 23 INVENTOR. JOHN L. MCCLURE Jan. 12, 1965 J.L. MCCLURE 3,165,593

ARC-'SUPPRESSING MULTIPOSITION ELECTRIC SWITCH 2 Sheets-Sheet 2 FiledAug. 14, 1961 JOHN L. Mc CLURE.

BY W United States Patent 3,165,598 ARC-SUPPRESSHNG MULTKPGSETifiNELECTREC SWlTCl-ll John L. McClure, Berwyn, IlL, assignor to GeneralElectric Company, a corporation of New York Fiied Aug. 14, 1961, Ser.No. 131,393 4 (Ilaims. (Cl. ass-s This invention relates to electricswitch devices, and in particular, to a multiple position switch forselecting any one of a plurality of different electric circuits.Although not in any sense restrictive thereto, a switch embodying theinvention is particularly useful in connection with the energization ofthe heating elements of an electric range. The invention affords aswitch which is of low cost, small size, and simple operation.

The conventional electric cooking range has a cooking surface on whichare supported a plurality of electric resistance heating elements knownin the art as surface cooking units; that is, the cooking units on whichare performed cooking operations involving broiling, frying and thelike. It is common practice to employ a S-heat switch and cooking unitshaving a pair of resistance heating elements. When the power sourcecomprises a threewire Edison 236-volt system, the cooking unit may beconnected into the available power circuit in any one of fiveheat-output conditions, ranging from maximum heat output wherein theheating elements are in parallel across 236 volts, to a minimum wattagecondition in which the two resistance elements are connected in seriesacross 118 volts.

Contemporary ranges utilize either a push-button type switch asexemplified by Andrews US. Patent 2,431,904, granted December 2, 1947 oran adaptation of the rotary switch typified by Illian US. Patent2,483,831, granted October 4, 1949. Each of these patents is assigned tomy present assignee; and in each case huge quantities of switchesembodying the respective inventions have been manufactured, sold, andvery successfully used.

Broadly peaking, each of these switches utilizes camming devices whichengage a movable contact and separate it from an associated fixedcontact when it is desired to break the electrical circuit into whichthe contacts are connected. In some situations a movable contact isdisengaged from one fixed contact and moved into engagement withanother, as part of the same switching operation. The push-buttonmechanism is quite complex, requiring at least four apertured or notchedplates of insulating material mechanically associated with several pushbuttons. The operation of the various buttons individually effectslongitudinal movement of the plates relativeto each other to bring aboutthe necessary co action of the movable and the fixed contact elements.The rotary switch is of simpler construction, although it requires arotating cam and push-pins operated thereby to accomplish the necessaryswitching actions.

A disadvantage of some stature in each of these switch types is that anelectric arc can generate as the contacts are separated. This can resultin deterioration of the contact elements and a shortening of theeffective life of the switch as a complete unit. I Also, the contactelements are not self-cleaning'and maytherefore accumulate dusty orgreasy deposits which increase the electrical resistance across thecontacts. e

It is an object of the present invention to provide a multi-positionelectric switch in which the switch actuat- I tion. The cam block ismounted upon a selection lever "ice ing mechanism protects againstcontact deterioration byutilizing a mechanism which, while eifectuatingthe contact separation, immediately interposes an insulating wall oftangible thickness between the fixed and the movable contact, thusreducing sparking to a minimum and providing a positive insulationbarrier rather than a mere air gap between the separated contacts.

It is another object of the invent-ion to provide a switching mechanismhaving a single lever by means of which the contact devices may beestablished in any of several possible electrical circuit relationships.

It is yet another object of the invention to provide a switchingmechanism having improved means for illuminating the designations orindices which identify each of the circuit conditions for which theswitch is designed.

It is a further object of the invention to provide a switch contactactuating means which effects a mechanical cleaning action in itsoperation of contacts between open and closed circuit positions.

In a presently preferred embodiment of the invention, a terminal boardof insulating material supports two parallel rows of terminal memberswhich project through the board. Certain of the terminal members havecontact base portions which extend inwardly of the board parallel to theundersurface thereof; other of the terminal members have spring contactelements or fingers extending into overlapping relation with the contactbases. Some of said spring contact elements may be above, and othersbelow, the adjacent contact bases. The elements are biased to engagewith the contact bases. A cam block of insulating material is disposedbetween the terminal rows and is guided for slideable movement parallelthereto. Said block has a plurality of longitudinally extending wallmeans which may engage a spring contact finger to separate it from acontact base by interposing itself therebetween, or may release apreviously separated contact finger for return to engagement with acontact base. The wall means are preferably of an inherently smoothmaterial such as nylon, and exert a rubbing action on the contactelements, thereby cleaning them at each operahaving an actuating knobextending forwardly of an escutcheon plate provided with transparentmarkings indicating the several circuit conditions which the switch mayestablish; and behind the escutcheon plate there is provided a lampsocket extending upwardly from a base fixed to the selection lever. Thelamp socket has a lightpassage aperture so arranged that as the levertraverses the plate from one to another of the markings, the markingimmediately front of the lamp socket is illuminated wherea'sthe adjacentmarkings are not. A feature. of interest in the invention resides in theuse of the lamp socket itself as a detent or indexing mechanism forcontrol of the movement of the lever from one to another operatingposition.

Other features and advantages of the invention. will be understood fromthe following description of a presently preferred embodimentthereof,-read in connection with the accompanying drawings in which: I

FIG. 1 is a front elevational view of a switch embodying the invention;

PEG. 2-is a side elevational view,.enlarged, and insection on lines 2-2of FIG. 3; v

FIG. 3 is a topplan viewof the assembled switch;

FIG. 4 is a top plan view of the frame and circuit selector leverassembly;

FIG; is a top plan view of the contact-actuating cam block;

FIG. 6 is a front elevational view of the cam block; FIG. 7 is a rearelevational View of the cam block;

FIG. 8 is aview of the cam block and terminal board assembly showingcontact positions with the selector lever in off position;

FIG. 9 is a rear elevational view showing the cam block and terminalboard with the selector lever in the oil position; and FIGS. 10 through14 are schematic representations of the five circuit conditionsobtainable with the switch in a three-wire Edison power source connectedto a twoelement heating unit.

Referring to FIGS. 2 and 4, the five heat switchl constituting apresently preferred embodiment of the invention, comprises a main framestructure 2 providing a base plate 3 having laterally spaced upstandingrear wall portions 4 and 5 separated by a substantially triangular baseportion 6. A slot 7 in said base portion 6 slideably accommodates a pin8 extending therethrough from the rear of the circuit-selector lever 10.Base plate 3 is also provided with an arcuate guide slot 12 whichslideably accommodates a pin 13 extending from the lever 10. Immediatelyin advance of the guide slot 12 an intermediate portion of the baseplateis formed into an up standing transverse wall 14 which is parallel tothe walls 4 and 5; said selector lever extends through a slot (notshown) having a length. suflicient to accommodate the movement of thearm throughout the several operating positions of theswitch. The rearwall portions and the wall 14 are formed with the upwardly extendingtabs, respectively 4.1, 5.1, 14.1 and 14.2, by means of which a terminalboard and associated mechanism are fixed relative to the base plate. Thefront of the base plate has separately extending leg portions 15, 16 towhich the front escutcheon plate 18 (FIG. 1) is fixed by any.

suitable means such as the integral studs .19 and fasteners 20. Plate 18is fitted with a transparent window 21 having on its rear an opaquescreen arranged to provide, in transparent letters, the indicia Hi, 2,3, Lo

and Wm to designate the five heats possible when the 7 switch isconnected across a conventionalv three-wire 236-volt A.-C. Edison powersource and supplying power to a two-unit resistance heater common in thesurface cooking units of electric cooking ranges. The escutcheon plateitself is provided with the oil marking indicating completedisconnection of thepower leads from the conductors serving the heatingelements. The selector lever 10 projects through an elongated slot 18.1in the plate 18 and terminates in a knob 22. Said knob is advantageouslyshaped to provide a relatively sharp upper edge 23' which referencesagainst the several indicia as the handle traverses the escutcheonplate. In order more clearly to designate the position of the knob, theselector arm is provided with a light source positioned immediatelybehind the window.

The mounting for the light forms a part of an indexing or detent systemwhich accurately positions the selector lever 10 at various circuit.establishing stations. As best shown in FIGS. 2 and 3, the lever 10mounts immediately in front of the wall 1 4, an insulated uprightcylinder 24 of insulation material having a slot 25 immediately facingthe window. grees on each side of the longitudinal axis of the arm 10,whereby the narrow beam oflight permitted by the slot is suflicient toilluminate the index immediately in front of it but not to illuminatethe indices onieach side of it.

' The open-topped cylinder zd'accommodates a neon bulb 26; such as aGeneral Electric Company type NESl in end to the respective margins ofthe wall 14, as clearly appearsin FIG. 3.

The particular relationship of the lever ill to the slots '7 and 12provide for a rectilinear rather than an arcuate movement of the knob22, so that said knob is always immediately in front of the escutcheonplate regardless of the swinging movement of the arm ll). Thus, in anyadjusted position of the knob, the sharp upper edge 23 thereof isdirectly in front of the particular window index.

The several electrical circuits which may be established by the switchmechanism result from the transverse shifting of a cam block havinginsulating camming surfaces and walls which establish the variousmovable contact elements or fingers in engagement with, or in insulatedrelationship with, the various fixed contact bases.

The cam block is in operative engagement with the selector lever it andis guided for rectilinear movement parallel to the wall 14, as presentlyexplained. I

FIG. 3 shows the top plan view of a relatively heavy rectangularterminal board 30 which is supported on p the board are, from left toright, 34, 35, 36 and 37. As

is apparent, the respective groups of terminals are an ranged inparallel rows which are in turn parallel to the front wall i l ofthe'housing. The individual terminals extend through the terminal boardand are appropiately staked thereto to prevent vertical or laterialdisplacement therein.

These contact base portions comprise the fixed contacts of the switchmechanism. For example, terminal 32 has a base portion 32.1 whichextends rearwardly in ahorizontal plane; the terminal may be of brasswith a silver or other good conducting metal inlay (not shown) which.extends through the contact base. The contact base portions of other ofthe terminals, presently identified, would e of similar construction.Terminal 33 is of brass, and just below the terminal board 3% it has alaterally extending flexible contact finger 33.1 of switch spring stock,mounting at its free end a contact button which extends toward theinsert of the terminal contact base 32.1. Terminal 31 has near itsbottom a laterally extending flexible contact finger 31.1 of switchspring stock. At its free end it has a contact button which extendstoward the conducting metal insert of the terminal base 32.1. Aspresently explained, means are provided whereby either 7 or both, orneither, of the button contacts of the contact Said slot may comprehendabout 3% de-' fingers may engage with the contact base 32.1.

Of the terminals in the rear row, terminal 36 is similar to terminal 32in that it has a horizontal contact base 36.1 extending inwardly of theterminal board in parallel relationship to the undersurface thereof.Terminal 35 has a similar inwardly turned base 35.11 (FIG. 9) and italso has a laterally extending contact finger 35.2 provided with acontact button which extends toward the conduct-. ing metal inlay of theterminal base 36.1. The respec-.

tive bases 32.1, 35.1 and 36.1 occupy a common horizontal plane.extending contact finger 34.1 of switchspring stock having a contactbutton extending toward the conducting metal inlay of terminal base35.1. Terminal 3'? hasnear its base a laterally extending contact finger37.1 having. a contact button extending toward the conductingmetal inlayof the terminalbase 36.1; The inherent spring bias of the severalcontact fingers is such'that unless restrained the contact buttonsof'fin'gers 31.1 and 33.1 will respec- I tively engage with the lowerand the'upper surfaces of the conducting metal inlay of terminal base 32.1; the con tact buttons of fingers 37.1 and 35.2,will respectively en-Certain of the terminals have contact base portions which extendinwardly of the terminal board in parallel relationship to theundersurface thereof.

Terminal 34 has near its base a laterally gage with the upper and lowersurfaces of the metal inlay of the terminal base 36.1; and the contactbutton of contact finger 34.1 will engage with the inlay of terminalbase 35.1.

The actuation of the respective contact fingers is controlled by thepositioning of various insulating wall members extending from thelongitudinal sides of the cam block 40, shown best in FIGS. 5, 6 and 7.Said cam block may be formed of superimposed pieces secured together byrivets or the like, or may be an integral body molded or otherwisedevised, from an insulating material such as nylon, which has aninherently smooth or lubricous surface. A stud 41 symmetrically arrangedrelative to the overall base dimensions of the block 40 is arranged :toride slideably within a slot 42 in the selector lever 10, whereby thereis no conflict between rectilinear movement of the block Miami theswinging movement of the lever. The upper wall portions 43, 44 (FIG. 5)engage with guides such as the studs 45, 46 (FIG. 2) whereby the camblock is accurately guided for rectilinear movement parallel to wall 14as the selector lever traverses the slot 18.1. Advantageously, there arefour such studs appropriately arranged for maximum guidance. In FIG. 6,which pictures the cam face looking toward the wall 14, there areillustrated five horizontally projecting wall portions arranged in upperand lower groups to define therewith a horizontal slot or guideway 48within which will ride the base portion 32.1 of terminal 32. The

upper group of said walls comprises an elongated wall 50 having adownwardly sloping cam surface 51; a short wall 52 having the upwardlysloping cam portion 53 and the downwardly sloping portion 54; and ashort end wall 55 having the upwardly sloping camming wall 56. The threewalls are separated by the two openings 57 and 58 through which thecontact portion'of contact finger 33.1 will pass to engage the contactbase 32.1 of terminal 32 under conditions of operation later described.The lower wall 60 has an upwardly sloping cam face 61; the lower wall 62has a downwardly sloping cam face 63 and an upwardly sloping face 64.The elongated space 65 accommodates movement of the contact fingersunder various circuit selection conditions. The reverse of the cam block41) (FIG. 7) similarly has groups of upper and lower walls, separated bya longitudinal slot 67 within which ride the contact bases 35.1 and36.1. For example, a relatively short upper wall-68 has the sloping face70; a gap 71 separates wall 68 from the longer wall 72 having the camface 73. The lower wall group comprises-the elongated wall 74 withits'illustrated sloping end faces and a short wall 75 with appropriatelysloping ends. The gap 76 between the walls 74 and 75 and the opening 77to the left of wall 74 accommodate contact finger movement. It will beunderstood, of course, that the variously identified cam faces orsloping walls are for the purpose of insuring a quick but not abruptseparation of the several contact finger contact buttons and to quicklyinterpose an insulating wall between the spaced contacts to prevent anypossibility of destructive arcing. Quite importantly, the movement ofthe various wall members along the faces of the contact buttons, and insome degree, at least, along the operating faces of the contact baseportions, serves to wipe these contact elements clean of any dust orgrease accumulations.

FIGS. 8 and 9 represent the contact relationships when the selectorlever 16 has moved block 40 to its off position. In FIG. 8 it is notedthat the contact fingers 33.1 and 31.1 areisolated from the contact base32.1 by the insulating walls 50 and 60 respectively; and according toFIG. 9 the contact base 35.1 is insulated from contact fingers 34.1 and35.2 by the respectivewalls 74 and 72,

and contact base 36.1 is insulated from the contact fingers 35.2and'37.1 by the interposedwalls 72 and 75.

FIGS. through 14 illustrate schematically the relationship of theseveral contact fingers and terminal contact base portions to producethe several circuit conditions within the scope of the illustratedswitch embodiment. It will be noted that for simplicity of illustrationthe contact elements and the several insulating wall members do notoccupy precisely the same relationship in the schematic figures as inthe illustration of the cam block. Terminal 32 is arranged forconnection to line conductor L1; terminal 37 is connected to lineconductor L2 and terminal 35 is connected to neutral conductor N. Theload is illustrated as comprising resistance elements R1, R2 of asurface heating unit of electric range or the like. In the circuitdiagrams, resistance elements energized across 236 volts are shown inheavy line; when across 118 volts are shown in light line; and whendeenergized are shown in dotted line. The 118-volt connection to thepilot light 26 has been detailed only in FIG. 10.

FIG. 10 shows the elements R1 and R2 at Hi heat; that is, each isenergized in a parallel circuit across L1 and L2. The circuit can betraced from L1 to contact base 32.1 and then by way of the respectivecontact fingers 31.1 and 33.1, which jointly make contact with contact32.1, to terminal 33 connected to an end terminal of R 1 and to terminal31 connected to an end terminal of R2. L2 is connected to terminal 37,whereupon by way of its contact finger 37.1 and contact base 36.1 ofterminal 36 to the juncture of R1 and R2. As shown by the broken line,terminal 34 is open relative to R2 by way of the interposition of theinsulating wall 74 between the contact of finger 34.1 and the contactbase 35.1 of terminal 35. Similarly, the neutral terminal contact finger35.2 is isolated from contact base 36.1 by interposition of insulatingwall 68. The pilot light is energized between the neutral line andterminal 33 by the obvious circuit.

For second heat, represented by FIG. 11, load element R1 is energizedacross 236 volts whereas element R2 is deenergized. Contact finger 33.1is insulated from line terminal contact base 32.1 by way of theinsulating Wall 52 therebetween. Thus, the right-hand terminal of R2 isdisconnected from power. The lefit-hand terminal of R1 is connected toL1 by way of the contact finger 31.1 and the contact base 32.1 of lineterminal 32. The junction terminal of R1 and R2 is connected to L2 byway of contact 36.1 and finger 37.1 of line terminal 37. Finger 34.1 ofterminal 34 is insulated from the neutral contact base 35.1 by way ofthe insulating wall 74 and the neutral terminal contact finger 35.2 isinsulated from contact 36.1 by the interposition of insulating wall 68.

For third heat represented by FIG. 12 the respective load elements R1and R2 are in parallel across 118 volts. The respective end terminals ofthe resistance elements are each connected to line L1 by way of thecontact fingers 31.1 and 33.1 which jointly engage the line terminalcontact base 32.1. The junction terminal of said resistances isconnected to the neutral line by way of the engagement of the neutralterminal contact finger 35.2 and the load terminal contact element 36.1.As is illustrated, the insulating wall 74 isolates the load terminal 34and its contact finger 34.1 from the neutral terminal contact base 35.1and isolates the line terminal L2 from the load contact element 36.1.

FIG. 13 illustrates the L0 circuit arrangement whereby the singleresistance element R1 is connected across 118 volts. The switchingarrangement differs from that of the FIG. 12 only in the sense thatinsulating wall 50 has been interposed between the contact finger 33.1and the load terminal contact finger 32.1.

FIG. 14 illustrates the warm circuit arrangement tral terminal contactfinger 35.2 from the load terminal contact element 36.11., and the upperinsulating wall 72 has interposed itself between the load terminalcontact 326.1 and the line terminal contact finger 37.1.

It will thus be apparent from the foregoing description that theillustrated switch embodiment provides for selection among a pluralityof possible electric circuits by a simple arm mechanism having arelatively short travel between its maximum heat and its off positions.The compactness of the switch will be understood when it is consideredthat F168. 1, 3 and 4 are full size represent-ations of an actual rangesurface unit control switch constructed according to the presentinvention, and that FIGS. 5, 6 and 7 are full scale drawings of the camblock as.

While there has been described what is at present thought to be apreferred embodiment of the invention,

' it will be understood that it is intended to cover in the appendedclaims all modifications which fall within the true spirit and scope ofthe invention.

What is claimed is:

1. A switching device for selecting an electric circuit from among aplurality of possible circuits, comprising. in combination, a terminalboard; a plurality of electric terminals spaced about said terminalboard and extend- I ing therethrough, certain of said terminals havingend portions constituting fixed contact elements occupying a commonplane, other of said terminals having means providing spring contactsoverlying certain of said fixed contact elements and still others havingmeans providing spring contacts extending beneath certain of said fixedcontacts, all of said spring contacts being biased to assome a normallyclosed circuit relationship with the associated fixed contact elements;a cam block; means for mounting said cam block for longitudinal slidingmovement in a plane parallel to said fixed contact elements; Said camblock including a body section and upper and lower insulating wallmembers extending laterally from said body section and collectivelyproviding a groove into which said fixed contact elements extend, saidWall members being positioned and formed to intrude between said fixedcont-act elements and spring contacts to separatethe same, said wallmembers, further, being provided at selected locations along theirlength with apertures through which spring contacts can reach theassociated fixe'd contact elements, whereby according to the lateraldisplacement of said cam block relative to said fixed contact elementsvarious electric circuit conditions may be established; and means foreffecting said cam block movement.

2. A switching device for selecting an electric circuit from among aplurality of possible circuits, comprising, in combination, a terminalboard; an index plate extending vertically therefrom and having atspaced intervals therealong indicia for identifying the respectivecircuits; a plurality of electric terminals spaced about said terminalboard and extending therethrough, certain of said terminals having'endportions constituting fixed contact elements occupying a common plane,other of said terminals having means providing spring contacts overlyingcertain of said fixed contact elements, said spring contacts beingbiased to assume a normally closed circuit relationship' with theassociated fixed contact elements; a cam block; means for mounting saidcam block for longitudinal sliding movement in a plane parallel to saidfixed contact elements; said cam block including a body section and aninsulating wall member extending laterally from c said body section tointrude between said fixed contact 7 elements and said spring contacts,said wall member beg ing with said cam block for effecting said lateraldisplace-- ment, said lever having an indexing element for registr-ation with the respective indicia on said indexing plate and having amanually operable end portion projecting in front of said plate; andlever mounting means providing for substantially rectilinear movement ofsaid'indexing element in parallel relation to said index plate duringarcuate movement of said lever comprising a base plate having a straightslot formed therein perpendicularly to said index plate and a curvedslot formed therein between said straight slot and said index plate,said lever having pins extending into said slots so as to be guidedthereby, said curved slot being formed so that substantially a constantlength of lever end portion projects in front of said,

plate in all positions of said lever.

3. An electrical switching device comprising, in combination, structureproviding a base plate, a selector lever pivotally mounted on said baseplate for movement in the plane thereof, an insulating terminal boardfixed to said structure in spaced parallel relation to the plane ofoperation of said selector lever, at least one row of electricalterminals mounted on said board in a straight row, 1

each of said terminals being spaced from the other, at least one of saidterminals having a portion projecting inwardly of said terminal board inparallel spaced relation thereto, to provde a fixed switch contact andother terminals having flexible contact fingers disposed in overlappingrelation to said fixed switch contact on opposite sides thereof, anactuating block of insulating material, said block including a bodysection and having a plurality of insulating walls projecting laterallyfrom said body section and arranged in upper and lower rows in a planeparallel to said terminal board, said fixed switch contact beingdisposed between said upper and lower rows and certain of said pluralityof walls in each of said upper and lower rows being spaced one from theother a sutlic-ient distance to permit said spring contact fingers toengage with said fixed switch contact, means for mounting said actuatingblock for movement relative to said line of terminals for selectiveinterposition of said actuating block walls between said contactfinger-s and said fixed switch I contact, and means connecting saidlever and said actuating block for movement of said block by said lever.

4-. A switching device for selecting an electric, circuit from among aplurality of possible circuits, comprising, incombination, structureproviding a base plate, an indcx plate mounted thereon, said index platehaving along its length a successioniof light-permeabale indic-iaindividually identifying the several possible circuits, a terminal boardof insulation material, means for mounting said terminal board in spacedrelation to said base plate, terminal members carried by said terminalboard and providing fixed contact elements, terminal members carried bysaid terminal board andproviding movable contact elements forcooperation with said fixed contact elements in establishing any of theplurality of possible circuits, an actuating member movable relative tosaid fixed and movable contacts to operate said movable contacts into adesired relationship to said fixed contacts, a lever pivotally mountedon said base plateand arranged to traverse said index plate whenpivoted, means engaging said actuating member with said lever to effectmovement of said member, detent means fixed relative to said indexplate, said detent means comprising a spring strip extendinglongitudinally behind said index plate and having a series ofundulations, each one of which represents a position of said actuatingmember establishing a particular electric circuit condition, means onsaid lever cooperating with said detent means to lyieldably positionsaid lever in registry with any of said circuit-identifying meanscomprising lamp means mounted on said lever for movement therewith, saidlamp means includingfa cylindrical lamp housing disposed rearwardly ofsaid index plate, said housing having a relatively narrow light passagewhereby to illuminate only the circuit-identifying 9 10 indioia withwhich the lever comes into registry, said lamp 2,672,531 3/54 Stevenson200-4 housing releasably engaging Within an undul at-ion for the2,786,103 5/57 Bevins 200-151 X positioning of said lever relative tothe circui r-identifying 2,868,930 1/ 59 Pistey 200-153 indieia.3,117,207 1/64 Baldasare 200-167 FOREIGN PATENTS References Cited by theExaminer 327 933 7 /3 5 Italy UNITED STATES PATENTS 1,964,449 6/34Carlson 200*167 BERNARD A. GILHEANY, Primary Examiner. 2,081,827 5/37Lohe 200167 10

1. A SWITCHING DEVICE FOR SELECTING AN ELECTRIC CIRCUIT FROM AMONG APLURALITY OF POSSIBLE CIRCUITS, COMPRISING, IN COMBINATION, A TERMINALBOARD; A PLURALITY OF ELECTRIC TERMINALS SPACED ABOUT SAID TERMINALBOARD AND EXTENDING THERETHROUGH, CERTAIN OF SAID TERMINAL HAVING ENDPORTIONS CONSTITUTING FIXED CONTACT ELEMENTS OCCUPYING A COMMON PLANE,OTHER OF SAID TERMINALS HAVING MEANS PROVIDING SPRING CONTACTS OVERLYINGCERTAIN OF SAID FIXED CONTACT ELEMENTS AND STILL OTHERS HAVING MEANSPROVIDING SPRING CONTACTS EXTENDING BENEATH CERTAIN OF SAID FIXEDCONTACTS, ALL OF SAID SPRING CONTACTS BEING BIASED TO ASSUME A NORMALLYCLOSED CIRCUIT RELATIONSHIP WITH THE ASSOCIATED FIXED CONTACT ELEMENTS;A CAM BLOCK; MEANS FOR MOUNTING SAID CAM BLOCK FOR LONGITUDINAL SLIDINGMOVEMENT IN A PLANE PARALLEL TO SAID FIXED CONTACT ELEMENTS; SAID CAMBLOCK INCLUDING A BODY SECTION AND UPPER AND LOWER INSULATING WALLMEMBERS EXTENDING LATERALLY FROM SAID BODY SECTION AND COLLECTIVELYPROVIDING A GROOVE INTO WHICH SAID FIXED CONTACT ELEMENTS EXTEND, SAIDWALL MEMBERS BEING POSITIONED AND FORMED TO INTRUDE BETWEEN SAID FIXEDCONTACT ELEMENTS AND SPRING CONTACTS TO SEPARATE THE SAME, SAID WALLMEMBERS, FURTHER, BEING PROVIDED AT SELECTED LOCATIONS ALONG THEIRLENGTH WITH APERTURES THROUGH WHICH SPRING CONTACTS CAN REACH THEASSOCIATED FIXED CONTACT ELEMENTS, WHEREBY ACCORDING TO THE LATERALDISPLACEMENT OF SAID CAM BLOCK RELATIVE TO SAID FIXED CONTACT ELEMENTSVARIOUS ELECTRIC CIRCUIT CONDITIONS MAY BE ESTABLISHED; AND MEANS FOREFFECTING SAID CAM BLOCK MOVEMENT.